The present invention writes generally to digitizing input devices and, more particularly, the present invention relates to the utilization of a magnetic random access memory (MRAM) device as a digitizing array within a digitizer apparatus that is integrated with a display system.
Digitizer systems are well known to those skilled in the art. Typically, an electromagnetic array, or other type of system, is responsive to a stylus used by a user to enter data directly upon a grid and to control various computer functions by writing, sketching, or pointing the stylus against the digitizer array. Some embodiments locate the digitizer directly on the monitor; other embodiments separate the two devices. Usually, separate digitizers are utilized where a large work surface is needed compared to the size of the display device such as a monitor screen. Integrated digitizer and display devices are utilized where portability and size are important. As such, various types of computer systems utilize stylus-based technologies and may include portable systems, desktop systems, transportable, or terminal-based systems.
The integrated digitizer-display systems are integrated only in the sense that they are coplanar and are fitted together in a common device. They are not integrated in that a signal processor is required to convert the signals generated by the digitizer into display signals compatible with the display. Thus, additional circuitry and complexity are involved in even the simplest of digitizer-display systems that are integrated for direct input on the same display surface where the digitizer is located.
Several types of stylus input digitizing devices exist in the prior art. One type involves direct contact of a stylus tip against a capacitive-resistive array. As the stylus tip, such as a metal tip or even a user""s finger, is placed proximate a selected area of a digitizing pad, a capacitive-resistive circuit within the pad detects the placement of the stylus and computes its location according to well-known mathematical formulas of a grid-based array. Typically, the capacitive-resistive array is used over small areas in devices such as a portable digitizer screen or finger-sensitive mouse pad.
A second prior art system utilizes an electromagnetic digitizer that interacts with a magnetic-tipped stylus or electromagnetic field-generating stylus in entering data and performing actions desired by the user. The tip of the stylus interacts with the field on the digitizer to convey information and data from the user. Typically a grid of intersecting lines produces a field that can be either actively or passively modified by the field generated by the stylus. Crossing lines can sense the field of the tip to generate a responsive signal, or can produce a field altered by the stylus during interaction.
Another embodiment is that of a stylus having an RF transmitter to send signals to the digitizing array, which then detects the transmitted signals utilizing receiving circuits in the array. Alternatively, the pad locations may be coated and the RF signal generated by the stylus interact with the array and are received at a receiver within the stylus itself.
Further, an alternative embodiment may incorporate a light source, such as visible or infrared light placed within the tip of the stylus to reflect off the pad. The stylus uses an imaging device, such as a CCD camera, to detect optically the return signal, and hence the location where the stylus interacts with the digitizer. The system then processes and decodes the received signal and location in order to determine the appropriate information.
Each of these systems has had some success; however, each has limitations that make them difficult or undesirable to use. For example, the direct contact technology is subject to scratches and wear during normal operation and has low durability compared to other technologies.
The wire-grid electromagnetic technology is expensive to implement and requires many individual wires for greater resolution. Additionally, the electromagnetic digitizers typically require a planar magnetic material behind the wire-grid sensor to shield the system from stray magnetic effects. In portable uses, this makes the technology for the system implementing such technology heavier than necessary. In the light-based systems, the stylus needs to be corded to the digitizer array and the need for sophisticated electronics for producing the light source as well as the CCD camera must be incorporated and expanded to achieve such a stylus.
One disadvantage common to all the various types of prior art digitizing technologies is that the digitizing array must always be under power in order for interaction of the user""s stylus with the digitizer to be maintained. Further, the user must also save the information to long-term storage, such as the hard disk drive on the computing system, in order to preserve the content of the user""s stylus session. Furthermore, in portable devices, the same can be said that the user""s input must be stored in long-term memory and cannot be maintained on the digitizer, typically which is overlayed with the displayed system so that the user can keep the most recent information upon restart of the apparatus unless power is provided to preserve the information in memory.
Digitizing arrays have been mated with display systems in order to provide an easy method of drawing and viewing the results simultaneously. For example, a digitizing array may be overlayed with an indium tin oxide display panel such that if the user interfaces with the digitizer using the stylus, the images displayed immediately under the stylus as the user interacts therewith. This enables the user to interact with the screen as if interacting with real data or writing on an actual writing tablet using a pen. Such technologies always require the use of an input signal processor, which coordinates with the digitizer to receive the user""s input via electromagnetic pulses, light pulses, resistive interaction or the used system to process the signals for display on the display apparatus portion.
Accordingly, what is needed is an improved digitizing apparatus that has greater resolution than the prior art systems, is easier to manufacture, and is more durable during actual use. Further, what is required is a digitizer apparatus that can be integrated with a display device and that can be manufactured with such a display as an electroluminescence apparatus using the same processing methods and techniques.
According to the present invention, an integrated digitizing tablet and display apparatus is disclosed. The digitizing tablet portion of the apparatus is comprised of an array of magnetic random access memory (MRAM) cells, wherein each MRAM cell is responsive to an externally applied magnetic field. Each memory cell has a magnetic bit that changes orientation upon application of an externally applied magnetic field to produce an electrical signal based on the orientation of the bit when a second electric field is applied across the array. The display is comprised of an array of pixel cells wherein each pixel cell is coupled to one of the MRAM cells and is activated by the electrical signal produced by the MRAM cell coupled thereto. Thus, what is achieved is an integrated digitizing tablet and display wherein the digitizing cells directly control the display cells without the need for additional processors. Further, the magnetic field may be either a fixed or varied field as generated by the interaction of a stylus that has either a fixed-field tip or a current-carrying tip to provide a varying field. Further still, the stylus may interact with the MRAM array to indicate an action to be performed by a computer system typically associated with the integrated digitizing tablet and display. The actions typically are those known in the art such as a right mouse click, a left mouse click, or other select functions and features. In one embodiment, the display portion is a thin film transistor display, but other transistor-based display systems may also be implemented.
The invention further includes a method of converting user input into image data within the integrated digitizing tablet and display of the present invention. Thus, the method includes providing an integrated array of MRAM cells and pixel cells, each MRAM cell having a magnetic bit that changes orientation upon application of a magnetic field and each cell being further coupled to one pixel cell, applying a magnetic field to the array to change the magnetic bit orientation of at least a portion of the MRAM cells, applying an input electric signal to the array, and activating the pixel cells coupled to the affected MRAM cells to display an image. The method may also include the application of a second magnetic field, independent of the first magnetic field, to change the magnetic bit orientation of at least a second portion of the MRAM cells to offer greater flexibility or to enable a second user to interact with the display digitizing assembly in concert with the first user. More than two magnetic fields may be applied and processed independently of one another.
An additional embodiment of the present invention includes an integrated digitizing and display cell. This integrated cell includes an MRAM cell actively coupled to a display pixel cell, wherein the functionality of the MRAM cell controls the functionality of the display cell directly without the need for further processing of the contents of the MRAM cell.